1. Field of the Invention
This invention relates to a constant molten metal surface level retaining furnace integrally provided with a melting unit wherein the melting unit and a retaining unit for storing molten metal to be delivered to a casting machine such as a die casting machine while keeping the molten metal surface level constant are of an integral structure.
2. Description of the Prior Art
Hitherto, molten metal delivered to a casting machine such as die casting machine, etc. is stored within a holding furnace so that temperature of molten metal is kept constant, and is then delivered to the casting machine by an electromagnetic pump, etc.
As a folding furnace of this kind, a heat retaining furnace having constant molten metal surface level retaining function to keep the level of the molten metal surface constant, is used. As such heat retaining furnace, there is known a heat retaining furnace with a float system having a vertically moving float that is moved in dependency upon downward movement of the molten metal surface level (Japanese Patent Publication No. 30787/1990). Another heat retaining furnace of a gas application type is known in which pressurized gas is delivered into a pressurized chamber within the heat retaining furnace so that the molten metal surface level is kept constant (Japanese Patent Application Laid Open No. 127962/1990).
In general, in the case of die casting an alloy, in such molten metal heat retaining furnace, materials are collectively melted at a portion within a central melting furnace, and are delivered to heat retaining furnaces of respective die casting machines by means such as a molten metal distribution (delivery) vehicle, etc.
On the contrary, in high quality die casting using aluminum alloy, there are many instances where the central melting furnace cannot be utilized. Therefore, dedicated melting furnaces are provided for every die casting machines.
As a melting furnace of this kind, there are known a melting furnace of a inclination pouring type to pour molten metal into the heat retaining furnace in a state where the furnace is inclined, and a melting furnace to deliver molten metal into the heat retaining furnace by using a gutter. As described above, in the case where molten metal heat retaining furnaces and dedicated melting furnaces are respectively provided in die casting machine units, there are a problem of space for installation and a problem of degradation of the quality of the molten metal which takes place accompanied by low efficiency in the process where molten metal is transferred from the melting furnace to the heat retaining furnace. Particularly, in high quality die casting, the latter causes the problem seriously.